Two-stage Setup Research Articles

Unlocking superior performance of broadband powerful mid-IR optical parametric amplifiers with a BaGa2GeS6 crystal pumped at 1.24 µm.

We report on the development of a tunable (1.5-6.5 µm) femtosecond optical parametric amplifier (OPA) based on a novel, to the best of our knowledge, BaGa2GeS6 (BGGS) crystal with a Cr:Forsterite pumping laser. Total conversion efficiency as high as 28% is achieved in a robust two-stage setup resulting in the generation of a 340-µJ 1.67-µm signal and 100-µJ 4.65-µm idler pulses. A 5-optical-cycles 94-fs 6-µm idler pulses are demonstrated with a propriate dispersion compensation by Ge and GaAs plates. An experimental estimate is given for the effective nonlinearity of a BGGS material, which for our nonlinear process reaches 19.5 pm/V for Type II phase matching. The crystal is additionally tested as a final amplifier in a high-energy OPA, where total output reaches 1.2 mJ with more than 40% conversion efficiency. The demonstrated high nonlinearity, high damage threshold, and chemical stability of the polished surface make BGGS crystal an ideal candidate for the development of high-energy OPAs with multi-millijoule pumping lasers.

Photoproton Production of 99m Tc and Its Theranostic Counterpart 101Tc via (γ,p) Reaction on Ruthenium

A production route for 99mTc and 101Tc using the (γ,p) reaction was considered. For an electron beam with energy of 40 MeV and power of 10 kW, distributions of produced 99mTc and 101Tc were obtained. For the optimized target (0.5 g) configurations, values of 99mTc specific activities of 9.53 GBq/g (0.26 Ci/g) for a one-stage setup and of 1.77 GBq/g (0.049 Ci/g) for a two-stage setup were obtained. For 101Tc, the corresponding values were 6.51 GBq/g (0.18 Ci/g) and 1.24 GBq/g (0.033 Ci/g).

Municipal Wastewater Treatment uses Vertical Flow Followed by Horizontal Flow in a Two-Stage Hybrid-Constructed Wetland Planted with Calibanus hookeri and Canna indica (Cannaceae).

The online version contains supplementary material available at 10.1007/s11270-022-05984-0.

Membranes for Carbon Dioxide Capture from Kuwait Power Stations:Process and Economic Analysis

Power plants account for 42% of the total emitted carbon dioxide in Kuwait. To reduce global warming, it is necessary to capture carbon dioxide from the flue gas of power stations. In this paper, commercial polyethylene-oxide based membranes were simulated using a two-stage setup for the production of a stream containing 90 mol% of carbon dioxide. The compression and the vacuum systems were evaluated in this study in terms of the membrane area, flow of the captured carbon dioxide, power consumption, and capital investment. Results show that the compression system requires less membrane area but it was not economical due to the high energy requirement of the compressor. In the vacuum system, the membrane area increased by a fold of 30 but the energy consumption was reduced by 96%. It was concluded that the vacuum system reduced the capital cost by 63% in contrast with the compression system. Compared to other technologies such as amine scrubber and pressure swing adsorption, the vacuum membrane system can provide a very attractive solution for carbon dioxide separation with a capture cost of 30.1$ per ton.

A two-stage dissolved air flotation saturator configuration for significant microbubble improvement

ABSTRACT The presence of suspended contaminants in water and wastewater, such as algae, colloids, fats and oil, necessitates the use of systems such as dissolved air flotation (DAF) for their removal. In the current study, a novel setup has been proposed for bubble enhancement. An industrial scale (pilot) DAF system was tested at saturator pressures of 3–7 atm and flow rates of 5–20 L/min in three different configurations, namely, empty, packed, and the innovative two-stage (TS) configuration. In the TS system, after the nucleation of micro bubbles, the water is returned to the saturator to undergo pressurization for a second time before it is passed through the nozzle once more and is released. The results show that the highest volume of released air as well as the smallest microbubbles are seen in the TS configuration, followed by packed mode, with the empty configuration showing the least favourable results. Moreover, the bubbles produced at the lowest residence time and pressure (3 atm) with the novel setup are better than the bubbles produced by the standard configuration, even with pressures as high as 7 atm. Thus, the novel TS setup can allow for significantly lower energy requirements and lower capital costs. For real-world application of the TS system, the feed for the saturator could be extracted from within or near the contact zone, i.e. where the bubbles are released in the DAF tank.

Modelling and analysis for biogas production process simulation of food waste using Aspen Plus

Researchers around the world are earnestly investigating the production of biogas from food waste as it is rich in organic content, and it has high potential to become a sustainable source for second-generation biofuels. The anaerobic digestion process is used to produce biogas but due to its complex nature, the process is still not efficient and productive. Current research on the production of biofuel out of food waste using two-stage digesters has shown promising results in increasing the biogas production rate and methane yield. Existing literature demonstrates only a few studies that have simulated a two-stage digester setup at thermophilic conditions for the anaerobic digestion of food waste at different fat concentrations, organic loading rates variation, and hydraulic retention times. Therefore, the purpose of this research was to simulate the anaerobic digestion of food waste using Aspen Plus at increasing Organic Loading Rates and Hydraulic Retentions Time and using 3 different fat concentration levels (20%, 40%, and 60%). The simulation used a two-stage digester setup at thermophilic (55 °C) conditions. The Aspen Plus simulation results demonstrated that at an Organic Loading Rate of between 2 l/day and 5 l/day and at a fat concentration level of 40% and 60%, the highest methane content achieved was 74.82% and 77.10%, respectively. The simulation results provided the data that can be used for future experimental projects for biogas research and development at an industrial level.

Nanosecond pulsed single-frequency two-stage holmium-doped fiber MOPA at 2054 nm and 2090 nm.

A single-frequency polarization-maintaining holmium-doped fiber master oscillator power amplifier operating at signal wavelengths of $2054\;{\rm nm}$ and $2090\;{\rm nm}$ is presented. The two-stage setup delivers up to $240\;{\rm W}$ peak power and $6.7\;\unicode{x00B5} {\rm J}$ pulse energy for a pulse width of $30.2\;{\rm ns}$ at a repetition rate of $100\;{\rm kHz}$. The first amplifier stage is designed by simulation, tailored for high gain at the signal wavelength range, favoring amplification at $2090\;{\rm nm}$. The design is discussed, and the measured values are compared with the simulation. The second stage is investigated regarding the efficiency for co- and counter-pumping. Stimulated Brillouin scattering was found to be the limiting factor for pulse peak power scaling in the second stage. The measured output pulse shapes are discussed and compared to pulse shapes derived with the Frantz-Nodvik model.

On Two-Stage Guessing

Stationary memoryless sources produce two correlated random sequences Xn and Yn. A guesser seeks to recover Xn in two stages, by first guessing Yn and then Xn. The contributions of this work are twofold: (1) We characterize the least achievable exponential growth rate (in n) of any positive ρ-th moment of the total number of guesses when Yn is obtained by applying a deterministic function f component-wise to Xn. We prove that, depending on f, the least exponential growth rate in the two-stage setup is lower than when guessing Xn directly. We further propose a simple Huffman code-based construction of a function f that is a viable candidate for the minimization of the least exponential growth rate in the two-stage guessing setup. (2) We characterize the least achievable exponential growth rate of the ρ-th moment of the total number of guesses required to recover Xn when Stage 1 need not end with a correct guess of Yn and without assumptions on the stationary memoryless sources producing Xn and Yn.

Self-Amplification of Coherent Energy Modulation in Seeded Free-Electron Lasers.

The spectroscopic techniques for time-resolved fine analysis of matter require coherent x-ray radiation with femtosecond duration and high average brightness. Seeded free-electron lasers (FELs), which use the frequency up-conversion of an external seed laser to improve temporal coherence, are ideal for providing fully coherent soft x-ray pulses. However, it is difficult to operate seeded FELs at a high repetition rate due to the limitations of present state-of-the-art laser systems. Here, we report a novel self-modulation method for enhancing laser-induced energy modulation, thereby significantly reducing the requirement of an external laser system. Driven by this scheme, we experimentally realize high harmonic generation in a seeded FEL using an unprecedentedly small external laser-induced energy modulation. An electron beam with a laser-induced energy modulation as small as 1.8 times the slice energy spread is used for lasing at the seventh harmonic of a 266-nm seed laser in a single-stage high-gain harmonic generation (HGHG) setup and the 30th harmonic of the seed laser in a two-stage HGHG setup. The results mark a major step toward a high-repetition-rate, fully coherent x-ray FEL.

Compact and robust supercontinuum generation and post-compression using multiple thin plates

Abstract We report on compact and robust supercontinuum generation and post-compression using transmission of light through multiple thin solid plates at the SwissFEL X-ray free-electron laser facility. A single stage consisting of three thin plates followed by a chirped mirror compressor achieves compression of initially 30-fs pulses with 800-nm center wavelength to sub-10-fs duration. We also demonstrate a two-stage implementation to compress the pulses further to sub-5-fs duration. With the two-stage setup, the generated supercontinuum includes wavelengths ranging from 500 to 1100 nm. The multi-plate setup is compact, robust, and stable, which makes it ideal for applications at free-electron laser facilities such as pump-probe experiments and laser-arrival timing tools.

High-energy γ -photon polarization in nonlinear Breit-Wheeler pair production and γ polarimetry

The interaction of an unpolarized electron beam with a counterpropagating ultraintense linearly polarized laser pulse is investigated in the quantum radiation-dominated regime. We employ a semiclassical Monte Carlo method to describe spin-resolved electron dynamics, photon emissions and polarization, and pair production. Abundant high-energy linearly polarized gamma photons are generated intermediately during this interaction via nonlinear Compton scattering, with an average polarization degree of more than 50%, which further interacting with the laser fields produce electron-positron pairs due to nonlinear Breit-Wheeler process. The photon polarization is shown to significantly affect the pair yield by a factor beyond 10%. The considered signature of the photon polarization in the pair's yield can be experimentally identified in a prospective two-stage setup. Moreover, the signature can serve also for the polarimetry of high-energy high-flux gamma photons with a resolution well below 1% with currently achievable laser facilities.

Harnessing Adaptive Evolution to Achieve Superior Mannitol Production by Lactococcus lactis Using Its Native Metabolism.

Mannitol can be obtained as a by-product of certain heterolactic lactic acid bacteria, when grown on substrates containing fructose. Lactococcus lactis, a homolactic lactic acid bacterium, normally does not form mannitol but can be persuaded into doing so by expressing certain foreign enzyme activities. In this study, we find that L. lactis has an inherent capacity to form mannitol from glucose. By adaptively evolving L. lactis or derivatives blocked in NAD+ regenerating pathways, we manage to accelerate growth on mannitol. When cells of the adapted strains are resuspended in buffer containing glucose, 4-58% of the glucose metabolized is converted into mannitol, in contrast to nonadapted strains. The highest conversion was obtained for a strain lacking all major NAD+ regenerating pathways. Mannitol had an inhibitory effect on the conversion, which we speculated was due to the mannitol uptake system. After its inactivation, 60% of the glucose was converted into mannitol by cells suspended in glucose buffer. Using a two-stage setup, where biomass first was accumulated by aerated culturing, followed by a nonaerated phase (static conditions), it was possible to obtain 6.1 g/L mannitol, where 60% of the glucose had been converted into mannitol, which is the highest yield reported for L. lactis.

Efficient production of \u03b1-acetolactate by whole cell catalytic transformation of fermentation-derived pyruvate

BackgroundDiacetyl provides the buttery aroma in products such as butter and margarine. It can be made via a harsh set of chemical reactions from sugarcane bagasse, however, in dairy products it is normally formed spontaneously from α-acetolactate, a compound generated by selected lactic acid bacteria in the starter culture used. Due to its bacteriostatic properties, it is difficult to achieve high levels of diacetyl by fermentation. Here we present a novel strategy for producing diacetyl based on whole-cell catalysis, which bypasses the toxic effects of diacetyl.ResultsBy expressing a robust α-acetolactate synthase (ALS) in a metabolically optimized Lactococcus lactis strain we obtained a whole-cell biocatalyst that efficiently converted pyruvate into α-acetolactate. After process optimization, we achieved a titer for α-acetolactate of 172 ± 2 mM. Subsequently we used a two-stage production setup, where pyruvate was produced by an engineered L. lactis strain and subsequently used as the substrate for the biocatalyst. Using this approach, 122 ± 5 mM and 113 ± 3 mM α-acetolactate could be made from glucose or lactose in dairy waste, respectively. The whole-cell biocatalyst was robust and fully active in crude fermentation broth containing pyruvate.ConclusionsAn efficient approach for converting sugar into α-acetolactate, via pyruvate, was developed and tested successfully. Due to the anaerobic conditions used for the biotransformation, little diacetyl was generated, and this allowed for efficient biotransformation of pyruvate into α-acetolactate, with the highest titers reported to date. The use of a two-step procedure for producing α-acetolactate, where non-toxic pyruvate first is formed, and subsequently converted into α-acetolactate, also simplified the process optimization. We conclude that whole cell catalysis is suitable for converting lactose in dairy waste into α-acetolactate, which favors resource utilization.

Use of a two-step process to denitrification of synthetic brines: electroreduction in a dual-chamber cell and catalytic reduction.

Membrane separation processes are being currently applied to produce drinking water from water contaminated with nitrate. The overall process generates a brine with high nitrate/nitrite concentration that is usually send back to a conventional wastewater treatment plant. Catalytic processes to nitrate reduction are being studied, but the main goal of achieving a high selectivity to nitrogen production is still a matter of research. In this work, a two-step process was evaluated, aiming to verify the best combination of operational parameters to efficiently reduce nitrate to nitrogen. In the first step, the nitrate was reduced to nitrite by electroreduction, applying a copper electrode and different cell potentials. A second step of the process was carried out by reducing the generated nitrite with a catalytic process by hydrogenation. The results showed that the highest nitrate reduction (89%) occurred when a cell potential of 11 V was applied. In this condition, the nitrite ion was generated with all experimental conditions evaluated. Then, to reduce the nitrite ion formed by catalytic reduction, activated carbon fibers (ACF) and powder γ-alumina (γ-Al2O3) were tested as supports for palladium (Pd). With both catalysts, the total nitrite conversion was obtained, being the selectivity to gaseous compounds 94% and 97% for Pd/Al2O3 and Pd/ACF, respectively. Considering the results obtained, a two-stage treatment setup to brine denitrification may be proposed. With electrochemistry, an operating condition was achieved in which ammonium production can be controlled to very low values, but the reduction is predominant to nitrite. With the second step, all nitrite is converted to nitrogen gas and just 3% of ammonium is produced with the most selective catalyst. The main novelty of this work is associated to the use of a two-stage process enabling 89% of nitrate reduction and 100% of nitrite reduction.

Catch Me If You Can: Testing the reduction of compound lotteries axiom in a tax compliance experiment

We test the Reduction of Compound Lotteries Axiom (RCLA) in an experiment on tax compliance. We disentangle the compound probability of audit and detection and test it against a more realistic situation with a probability of audit and a subsequent probability of detection. Various experiments have shown that abstract framing often leads to violations of the RCLA; our framed set-up also reveals statistically significant departures from the RCLA. We find that subjects comply more in the two-stage lottery set-up than they do in the one-stage equivalent and that violations are compatible with subjects applying different weighting functions to one-stage lotteries versus two-stage lotteries: inverse S-shaped - likelihood insensitive - in the former set-up; and significantly less insensitive in the latter. Violations substantially decline with subjects’ experience but not at the same rate for all groups of subjects.

Method for the Absolute Calibration of Direct-Current Current Transducers

This paper describes an absolute method for calibrating commercial 1000:1 dc current transducers (DCCTs). By adding two auxiliary windings to produce 10:1 and 100:1 ratios, we use a three-step build-up method to establish the 1000:1 current ratio standard. First, we determine the 10:1 ratios of 11 DCCTs through permutation; second, we set up a two-stage composite DCCT to produce a 100:1 ratio; after switching auxiliary windings in the two-stage setup, we then derive the 1000:1 current ratio. The experimental results show that the requirements for the current source and the current meter are not stringent; their Type-B contributions to the overall uncertainties are very small. Type-A uncertainties which include factors such as the experimental environment and possible drifts of the output offsets of the DCCTs are experimentally determined. Repeated tests show that the current ratio standard has an expanded uncertainty of $0.26 \times 10^{-6}$ for the 1000:1 ratio.

Fixed accuracy confidence interval on the common variance in compound symmetric multivariate normal sampling

This work deals with construction of fixed accuracy confidence intervals for the common variance in compound symmetric multivariate normal distribution by adopting a Stein-type two-stage setup and a completely sequential setup. Related asymptotics are developed and the procedures are evaluated by simulation study.

Phosphorus recovery from low phosphate-containing solution by electrodialysis

The use of electrodialysis to treat a low phosphorus-containing solution (0.011 g L−1 HxPO43-x) was evaluated aiming at the recovery of phosphorus from municipal wastewater. The study was held in galvanostatic mode using a five-compartment electrodialysis cell with two pairs of cation- and anion-exchange heterogeneous membrane. A two-stage electrodialysis setup was proposed to recover phosphorus from a low phosphate-containing municipal wastewater. At underlimiting current density conditions, a solution with a phosphate concentration higher than 0.100 g L−1 was obtained by consecutively changing the solution in the diluted reservoir after reaching a demineralization rate of 50.0%. A concentration factor of 9.7 was obtained and no significant changes that could compromise the efficiency of the process were observed. The phosphate ions of the concentrated solution could be then separated from coexisting ions, such as sulfate, by the employment of overlimiting current density conditions, with its feasibility dependent on the use of alkali resistance anion-exchange membranes.

TMP properties and refining conditions in a CD82 chip refiner. Part I: Step changes of process variables, description of the tests

Abstract The study explores how changes in process variables, residence time and pulp consistency in refining influence the pulp properties. The equipment utilized in this study was a conical disc chip refiner (RGP82CD) producing thermomechanical pulp (TMP). The focus was on the ratio between tensile index and specific energy consumption. Pulp properties were measured for composite pulp samples taken from the refiner blow line. Residence times and pulp consistencies were estimated by use of the extended entropy model. This showed that the CD-refiner, with the flat and conical refining zone, has a process performance similar to that of a two-stage refiner set-up, and that the consistency in both refining zones is of high importance. Comparing different periods revealed that even if the values of measured blow line consistency are similar, significant differences in the estimated consistency in the flat zone can prevail. Therefore, only monitoring blow line consistency is not enough. Specifically, it was found that the pulp consistency after the flat zone could be very high, considerably higher than in the blow line, and this could have negative effects on tensile index and fibre length.

Multimode EDFA With Scalable Mode Selective Gain Control at 1480-nm Pump Wavelength

Erbium-doped fiber amplifiers are a promising solution for the signal amplification in long-haul mode-division multiplexed transmission systems. In order to minimize signal degradations by these amplifiers, low mode dependent gain and noise figures are desirable. We propose a scalable mode dependent gain equalization scheme for the 1480-nm pump wavelength. Contrary to the 980-nm pump wavelength, each signal mode has a maximum overlap with only one pump mode. Due to this, a scalable mode selective gain control is achievable by adjusting the pump modes. In this letter, we demonstrate the scalability of our approach with the number of signal modes by numerical simulation. Furthermore, we propose a two-stage amplifier setup in which the mode dependent gain of both stages is compensated in the second stage, pumped at a wavelength of 1480 nm.